Bug 1573080 - Supporting indenting of directives in preprocessor.py. r=glandium

Depends on D41494

Differential Revision: https://phabricator.services.mozilla.com/D41495

--HG--
extra : moz-landing-system : lando

python/mozbuild/mozbuild/preprocessor.py

@@ -373,7 +373,7 @@ class Preprocessor:
         """
         self.marker = aMarker
         if aMarker:
-            self.instruction = re.compile('{0}(?P<cmd>[a-z]+)(?:\s+(?P<args>.*?))?\s*$'
+            self.instruction = re.compile('\s*{0}(?P<cmd>[a-z]+)(?:\s+(?P<args>.*?))?\s*$'
                                           .format(aMarker))
             self.comment = re.compile(aMarker, re.U)
         else:

python/mozbuild/mozbuild/test/test_preprocessor.py

@@ -179,6 +179,16 @@ class TestPreprocessor(unittest.TestCase):
             '#endif',
         ])
 
+    def test_indentation(self):
+        self.do_include_pass([
+            '         #define NULLVAL 0',
+            ' #if !NULLVAL',
+            'PASS',
+            '           #else',
+            'FAIL',
+            '     #endif',
+        ])
+
     def test_expand(self):
         self.do_include_pass([
             '#define ASVAR AS',